Soon after, he moved his stock of goods to Wilmington, where he sold out and entered the employ of Banning & Company as superintendent of the building of wharves and warehouses.
He became employed again by Banning & Co., as wagon master, and soon had general charge of their freight business and workshops, where he continued until after the American Civil War.
Later, this company made its headquarters at Los Angeles, where they built a feed mill at the corner of Molino and Palmetto streets and were organized as the McDonald Grain and Milling Company with a capital of $200,000, McDonald being the president and Keller the secretary and manager.
[1] October 19, 1865, McDonald married Miss Mary Hamilton Winslow of Washington County, New York.
He died after a lingering illness, at his home in Wilmington, on June 10, 1899, leaving no descendants, his wife alone surviving him.